Rigid body: how to display collision margin in Blender 3D?
If you mean you want to see the hitboxes of the objects with rigid bodies (the collision shape), you have to do nothing. Usually they are shown on top of the object. If you cannot see them, try to set the Viewport shader to in WireFrame. If you still cannot see the hitbox its because the shape box is set to Mesh, so it overlaps with the current mesh. If your intent was to see a bigger hitbox for objects with an higher collision margin. I don't know if that's possible.